The present invention relates to a driver circuit for a synchronous alternating-current motor.
More specifically, the subject of the invention is a driver circuit for a synchronous motor comprising a stator with at least one winding arranged around a substantially U- or C-shaped pack of magnetic plates between the pole ends of which a permanent- magnet rotor is mounted for rotation.
Alternating-current synchronous motors of this type are used, for example, for driving pumps such as pumps for aquariums or for household appliances.
A problem with these motors is that, upon starting, they typically develop a very low torque which is generally insufficient to overcome the resisting torque offered by the load, for example, the resisting torque of a pump rotor immersed in a liquid.
Various solutions, mostly of a mechanical nature, have been proposed for addressing this problem. For example, in one known solution, the rotor of the motor is disconnected from the load upon starting and is then connected thereto only after a certain angular displacement has been performed.
A coupling for achieving a mechanical connection of this type between the rotor and the load of a synchronous alternating-current motor is described, for example, in European patent application No. 0 207 430.
Couplings of this type, however, have the disadvantage of being quite noisy in operation.
The object of the present invention is to provide a driver circuit for a synchronous, alternating-current motor of the type specified above which addresses shortcomings associated with the prior art.